Boost your JavaScript knowledge with our JavaScript Cheat Sheet Challenges. From basic concepts to advanced topics, these challenges are designed to enhance your understanding and application of JavaScript in real-world scenarios.
Easy
1. Challenge: Write a JavaScript program to print “Hello, World!” to the console.
Answer:
console.log("Hello, World!");2. Challenge: Write a JavaScript function to find the sum of two numbers.
Answer:
function sum(a, b) {
return a + b;
}
console.log(sum(5, 10));
3. Challenge: Write a JavaScript program to check if a number is even or odd.
Answer:
const number = 7;
if (number % 2 === 0) {
console.log("The number is even.");
} else {
console.log("The number is odd.");
}
4. Challenge: Write a JavaScript function to reverse a string.
Answer:
function reverseString(str) {
return str.split('').reverse().join('');
}
console.log(reverseString("Hello, World!"));
5. Challenge: Write a JavaScript function to find the maximum of three numbers.
Answer:
function findMax(a, b, c) {
return Math.max(a, b, c);
}
console.log(findMax(3, 6, 2));
Medium
6. Challenge: Write a JavaScript function to count the number of vowels in a given string.
Answer:
function countVowels(str) {
const vowels = 'aeiouAEIOU';
let count = 0;
for (let char of str) {
if (vowels.includes(char)) {
count++;
}
}
return count;
}
console.log(countVowels("Hello World"));
7. Challenge: Write a JavaScript function to find the factorial of a number using recursion.
Answer:
function factorial(n) {
if (n === 0 || n === 1) {
return 1;
} else {
return n * factorial(n - 1);
}
}
console.log(factorial(5));
8. Challenge: Write a JavaScript function to check if a string is a palindrome.
Answer:
function isPalindrome(str) {
return str === str.split('').reverse().join('');
}
console.log(isPalindrome("racecar"));
9. Challenge: Write a JavaScript function to find the Greatest Common Divisor (GCD) of two numbers.
Answer:
function gcd(a, b) {
while (b) {
[a, b] = [b, a % b];
}
return a;
}
console.log(gcd(48, 18));
10. Challenge: Write a JavaScript function to find the second largest element in an array.
Answer:
function findSecondLargest(arr) {
const uniqueNumbers = [...new Set(arr)];
uniqueNumbers.sort((a, b) => b - a);
return uniqueNumbers[1];
}
console.log(findSecondLargest([1, 3, 4, 4, 5, 6, 6, 7]));
Hard
11. Challenge: Write a JavaScript function to implement the Fibonacci sequence using dynamic programming.
Answer:
function fibonacci(n) {
const fib = [0, 1];
for (let i = 2; i <= n; i++) {
fib[i] = fib[i - 1] + fib[i - 2];
}
return fib[n];
}
console.log(fibonacci(10));
12. Challenge: Write a JavaScript function to find all prime numbers up to a given number using the Sieve of Eratosthenes.
Answer:
function sieveOfEratosthenes(n) {
const primes = Array(n + 1).fill(true);
primes[0] = primes[1] = false;
for (let p = 2; p * p <= n; p++) {
if (primes[p]) {
for (let i = p * p; i <= n; i += p) {
primes[i] = false;
}
}
}
return primes.map((isPrime, index) => isPrime ? index : null).filter(Boolean);
}
console.log(sieveOfEratosthenes(30));
13. Challenge: Write a JavaScript function to implement a binary search algorithm.
Answer:
function binarySearch(arr, x) {
let low = 0, high = arr.length - 1;
while (low <= high) {
const mid = Math.floor((low + high) / 2);
if (arr[mid] === x) {
return mid;
} else if (arr[mid] < x) {
low = mid + 1;
} else {
high = mid - 1;
}
}
return -1;
}
console.log(binarySearch([1, 2, 3, 4, 5, 6, 7], 4));
14. Challenge: Write a JavaScript function to solve the “N-Queens” problem using backtracking.
Answer:
function isSafe(board, row, col, n) {
for (let i = 0; i < col; i++) {
if (board[row][i]) return false;
}
for (let i = row, j = col; i >= 0 && j >= 0; i--, j--) {
if (board[i][j]) return false;
}
for (let i = row, j = col; j >= 0 && i < n; i++, j--) {
if (board[i][j]) return false;
}
return true;
}
function solveNQueens(board, col, n) {
if (col >= n) return true;
for (let i = 0; i < n; i++) {
if (isSafe(board, i, col, n)) {
board[i][col] = 1;
if (solveNQueens(board, col + 1, n)) return true;
board[i][col] = 0;
}
}
return false;
}
const n = 4;
const board = Array.from({ length: n }, () => Array(n).fill(0));
solveNQueens(board, 0, n);
console.log(board);
10. Challenge: Write a JavaScript function to perform Merge Sort.
Answer:
function mergeSort(arr) {
if (arr.length <= 1) return arr;
const mid = Math.floor(arr.length / 2);
const left = mergeSort(arr.slice(0, mid));
const right = mergeSort(arr.slice(mid));
return merge(left, right);
}
function merge(left, right) {
let result = [], l = 0, r = 0;
while (l < left.length && r < right.length) {
if (left[l] < right[r]) {
result.push(left[l]);
l++;
} else {
result.push(right[r]);
r++;
}
}
return result.concat(left.slice(l)).concat(right.slice(r));
}
const array = [12, 11, 13, 5, 6, 7];
console.log("Sorted array:", mergeSort(array));
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